Camray 5 oil boiler reheating issue

[sdburg]

Morning All,

hopefully some here has experanced this isee as its driving me mad, My seven (ish will explain) year old boiler now won't reheat the water straight after running a bath(started doing this about a month ago) , it always used to. CH fine no issues, So here goes boilers on idle start running a bath, hot water comes through boiler ignites to heat water, water at the tap starts to go cold so I turn off the hot water and the boiler also turns off. What used to happen was the boiler would then reignite to heat the cold water up, but not now it just stays of, so I remove the front cover and take out the tank sensor and the boiler ignites and warms up the water, so your thinking its the sensor, heres the best bit, I have replaced all sensors, PCB board, Heat exchanger tank (6 months ago due to a previous unconnected issue) three way valve and head (the white bit) changes DHW switch, flow switch and the expansion tank . the only bits left of the seven year old boiler is the hot water tank its self. the burner and the heat exchanger plate.
As a side issue I live in a very hard water area eg descale new keetles after a week. I have been told it's possible that the hot water tank has scaled up, but want to check on here before replacing the tank as its not the easiest thing to get to.

many thanks for your help / ideas

S

 

[aqualogic7]

hot tank cannot be scaled up as only used as heat store, hot water is heated in plate exchanger. what flow rate are you getting through hot tap ?

 

[sdburg]

very good water pressure at the bath which is at the furthest point, house is upside down and the boiler is on the top floor baths downstair so not sure if gravity has anything to do with it. Will look at the plate exchanger. thanks

 

[kimbo]

Have you checked the temperature in the tank stat pocket with a temperature gauge

 

[sdburg]

no, but when I take the sensor out it very hot can't hold it. will get hold of one and test it,

 

[kimbo]

so if the store is hot , because the sensor is hot the issue is with the hot water in the store not circulating around the heat exchanger, unless there is air in the top of the store which has turned to steam and fooling the stat into thinking the water is up to temperature, I,ve had that with some boiers. First check all the store is hot not just the top,The stat is doing its job by the sound of it if its very hot in its pocket, if it is satisfied it wont allow the boiler to fire up but the pump should still run and circulate the water around the heat exchanger via the 3 port valve.
The pump is obviously working and the 3 port valve is working as it all works with the stat in the pocket. It would seem that the problem lies with the store and stat, the stat is obviously working but the problem must lie with the store being hot on the top only.

 

[sdburg]

intresting you say that about the air as the new hot water tank I have has an air release value on top but the current one doesn't. it just has a unpside down U shape copper bar with a scew in it whic I presume is to release air, going to give is a go now.

 

[sdburg]

ok talking out of my backside found the air vent at the back right of the hot water tank on the old one, its at the fron on the new one which is why I didn't think it had one, will update shortly

 

[sdburg]

ok thats effing hot water coming out of that vent think what I will do is replace the plate exchanger amd let you know what happens. many thanks S